oc types



  • oc types
    Concepts and Types 
    
    Kubernetes and OpenShift help developers and operators build, test, and deploy
    applications in a containerized cloud environment. Applications may be composed
    of all of the components below, although most developers will be concerned with
    Services, Deployments, and Builds for delivering changes. 
    
    Concepts: 
    
    * Containers:
        A definition of how to run one or more processes inside of a portable Linux
        environment. Containers are started from an Image and are usually isolated
        from other containers on the same machine.
        
    * Image:
        A layered Linux filesystem that contains application code, dependencies,
        and any supporting operating system libraries. An image is identified by
        a name that can be local to the current cluster or point to a remote Docker
        registry (a storage server for images).
        
    * Pods [pod]:
        A set of one or more containers that are deployed onto a Node together and
        share a unique IP and Volumes (persistent storage). Pods also define the
        security and runtime policy for each container.
        
    * Labels:
        Labels are key value pairs that can be assigned to any resource in the
        system for grouping and selection. Many resources use labels to identify
        sets of other resources.
        
    * Volumes:
        Containers are not persistent by default - on restart their contents are
        cleared. Volumes are mounted filesystems available to Pods and their
        containers which may be backed by a number of host-local or network
        attached storage endpoints. The simplest volume type is EmptyDir, which
        is a temporary directory on a single machine. Administrators may also
        allow you to request a Persistent Volume that is automatically attached
        to your pods.
        
    * Nodes [node]:
        Machines set up in the cluster to run containers. Usually managed
        by administrators and not by end users.
        
    * Services [svc]:
        A name representing a set of pods (or external servers) that are
        accessed by other pods. The service gets an IP and a DNS name, and can be
        exposed externally to the cluster via a port or a Route. It's also easy
        to consume services from pods because an environment variable with the
        name <SERVICE>_HOST is automatically injected into other pods.
        
    * Routes [route]:
        A route is an external DNS entry (either a top level domain or a
        dynamically allocated name) that is created to point to a service so that
        it can be accessed outside the cluster. The administrator may configure
        one or more Routers to handle those routes, typically through an Apache
        or HAProxy load balancer / proxy.
        
    * Replication Controllers [rc]:
        A replication controller maintains a specific number of pods based on a
        template that match a set of labels. If pods are deleted (because the
        node they run on is taken out of service) the controller creates a new
        copy of that pod. A replication controller is most commonly used to
        represent a single deployment of part of an application based on a
        built image.
        
    * Deployment Configuration [dc]:
        Defines the template for a pod and manages deploying new images or
        configuration changes whenever those change. A single deployment
        configuration is usually analogous to a single micro-service. Can support
        many different deployment patterns, including full restart, customizable
        rolling updates, and fully custom behaviors, as well as pre- and post-
        hooks. Each deployment is represented as a replication controller.
        
    * Build Configuration [bc]:
        Contains a description of how to build source code and a base image into a
        new image - the primary method for delivering changes to your application.
        Builds can be source based and use builder images for common languages like
        Java, PHP, Ruby, or Python, or be Docker based and create builds from a
        Dockerfile. Each build configuration has web-hooks and can be triggered
        automatically by changes to their base images.
        
    * Builds [build]:
        Builds create a new image from source code, other images, Dockerfiles, or
        binary input. A build is run inside of a container and has the same
        restrictions normal pods have. A build usually results in an image pushed
        to a Docker registry, but you can also choose to run a post-build test that
        does not push an image.
        
    * Image Streams and Image Stream Tags [is,istag]:
        An image stream groups sets of related images under tags - analogous to a
        branch in a source code repository. Each image stream may have one or
        more tags (the default tag is called "latest") and those tags may point
        at external Docker registries, at other tags in the same stream, or be
        controlled to directly point at known images. In addition, images can be
        pushed to an image stream tag directly via the integrated Docker
        registry.
        
    * Secrets [secret]:
        The secret resource can hold text or binary secrets for delivery into
        your pods. By default, every container is given a single secret which
        contains a token for accessing the API (with limited privileges) at
        /var/run/secrets/kubernetes.io/serviceaccount. You can create new
        secrets and mount them in your own pods, as well as reference secrets
        from builds (for connecting to remote servers) or use them to import
        remote images into an image stream.
        
    * Projects [project]:
        All of the above resources (except Nodes) exist inside of a project.
        Projects have a list of members and their roles, like viewer, editor,
        or admin, as well as a set of security controls on the running pods, and
        limits on how many resources the project can use. The names of each
        resource are unique within a project. Developers may request projects
        be created, but administrators control the resources allocated to
        projects.
        
    For more, see https://docs.openshift.com
    
    Usage:
      oc types [flags]
    
    Examples:
      # View all projects you have access to
      oc get projects
      
      # See a list of all services in the current project
      oc get svc
      
      # Describe a deployment configuration in detail
      oc describe dc mydeploymentconfig
      
      # Show the images tagged into an image stream
      oc describe is ruby-centos7
    
    Use "oc options" for a list of global command-line options (applies to all
    commands).
    

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